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Software
'Software' Computer software, or just software, is any set of machine-readable instructions that directs a computer's processor to perform specific operations. The term is used to contrast with computer hardware, the physical objects (processor and related devices) that carry out the instructions. Computer hardware and software require each other and neither can be realistically used without the other. Software is a general term. It can refer to all computer instructions in general, or to any specific set of computer instructions. It is inclusive of both machine instructions (the binary code that the processor "understands") and source code (more human-understandable instructions that must be rendered into machine code by compilers or interpreters before being executed). Computer software is a set of programs, procedures, functions, associated data and/or its documentation, if any. Program software performs the function of the program it implements, either by directly providing instructions to the digital electronics or by serving as an input to another piece of software. Software is also sometimes used in a more narrow sense, meaning application software only. Computer software is so called to distinguish it from computer hardware, which encompasses the physical devices and interconnections required to store and run ("execute") the software. In contrast to hardware, executable software exists as data in the computer system and hence "cannot be touched", just as the 3D model shown in the illustration cannot be touched."Wordreference.com: WordNet 2.0". Princeton University, Princeton, NJ. Retrieved 2007-08-19. At the lowest level, executable code consists of machine language instructions specific to an individual processor. A machine language consists of groups of binary values signifying processor instructions that change the state of the computer from its preceding state. For example, an instruction may change the value stored in a particular storage location inside the computer (an effect that is not directly observable to the user), or (indirectly) cause something to appear on a display of the computer system (a state change which should be visible to the user). The processor carries out the instructions in the order they are provided, unless it is instructed to "jump" to a different instruction, or interrupted. Software is usually written in high-level programming languages that are easier and more efficient for humans to use (closer to natural language) than machine language."Compiler construction" High-level languages are compiled or interpreted into machine language object code. Software may also be written in an assembly language, essentially, a mnemonic representation of a machine language using a natural language alphabet. Assembly language must be assembled into object code via an assembler. 'Types of software' A layer structure showing where the operating system software and application software are situated while running on a typical desktop computer Software encompasses a wide array of products that may be developed using different techniques such as ordinary programming languages, microcode, or an FPGA configurationneeded. On virtually all computer platforms, software can be grouped into a few broad categories: * System software is computer software designed to operate the computer hardware, to provid e basic functionality, and to provide a platform for running application software.^ "System Software". The University of Mississippi. System software includes device drivers, operating systems, servers, utilities, and window systems. System software also includes the boot firmware, which loads (or in some cases constitutes) the operating system. Firmware is software that has been permanently stored in hardware (specifically, in non-volatile memory). Thus, it has qualities of both software and hardware, but it is still software. * Application software and scripts were historically defined as all the software that uses the computer system to perform useful work (or entertainment functions) beyond the basic operation of the computer itself. However, in practice the distinction between system software and application software is often blurred due to bundling of useful applications with the operating system. Application software includes desktop applications such as web browsers and Microsoft Office, as well as smartphone and tablet applications (called "apps"). #Javascript scripts are pieces of software traditionally embedded in web pages that are run directly inside the web browser when a web page is loaded, without the need for a web browser plugin. Software written in other programming languages can also be run within the web browser if the software is either translated into Javascript, or if a web browser plugin that supports that language is installed; the most common example of the latter is ActionScript scripts, which are supported by the Adobe Flash plugin. #Web applications usually run on the web server and output dynamically-generated web pages to web browsers, using e.g. PHP, Java or ASP.NET, or even Javascript that runs on the server; in modern times they commonly include some Javascript to be run in the web browser as well, in which case they typically run partly on the server, partly in the web browser. * Plugins and extensions are software that extends or modifies the functionality of another piece of software, and require that software be used in order to function; * Embedded software resides as firmware within embedded systems, devices dedicated to a single use or a few uses such as cars and televisions (although some embedded devices such as wireless chipsets can themselves be part of an ordinary, non-embedded computer system such as a PC or smartphone).^ "Embedded Software—Technologies and Trends". IEEE Computer Society. Retrieved May/June 2009. In the embedded system context there is sometimes no clear distinction between the system software and the application software. However, some embedded systems run embedded operating systems, and these systems do retain the distinction between system software and application software (although typically there will only be one, fixed, application which is always ran). * Microcode is a special, relatively obscure type of embedded software which tells the processor itself how to execute machine code, so it is actually a lower level than machine code."Microcode". Princeton University. It is typically proprietary to the processor manufacturer, and any necessary correctional microcode software updates are supplied by them to users (which is much cheaper than shipping replacement processor hardware). Thus an ordinary programmer would not expect to ever have to deal with it. Software topics Architecture Users often see things differently than programmers. People who use modern general purpose computers (as opposed to embedded systems, analog computers and supercomputers) usually see three layers of software performing a variety of tasks: platform, application, and user software. * Platform software: Platform includes the firmware, device drivers, an operating system, and typically a graphical user interface which, in total, allow a user to interact with the computer and its peripherals (associated equipment). Platform software often comes bundled with the computer. On a PC you will usually have the ability to change the platform software. * Application software: Application software or Applications are what most people think of when they think of software. Typical examples include office suites and video games. Application software is often purchased separately from computer hardware. Sometimes applications are bundled with the computer, but that does not change the fact that they run as independent applications. Applications are usually independent programs from the operating system, though they are often tailored for specific platforms. Most users think of compilers, databases, and other "system software" as applications. * User-written software: End-user development tailors systems to meet users' specific needs. User software include spreadsheet templates and word processor templates. Even email filters are a kind of user software. Users create this software themselves and often overlook how important it is. Depending on how competently the user-written software has been integrated into default application packages, many users may not be aware of the distinction between the original packages, and what has been added by co-workers. 'Execution' Computer software has to be "loaded" into the computer's storage (such as the hard drive or memory). Once the software has loaded, the computer is able to execute the software. This involves passing instructions from the application software, through the system software, to the hardware which ultimately receives the instruction as machine code. Each instruction causes the computer to carry out an operation – moving data, carrying out a computation, or altering the control flow of instructions. Data movement is typically from one place in memory to another. Sometimes it involves moving data between memory and registers which enable high-speed data access in the CPU. Moving data, especially large amounts of it, can be costly. So, this is sometimes avoided by using "pointers" to data instead. Computations include simple operations such as incrementing the value of a variable data element. More complex computations may involve many operations and data elements together. 'Quality and reliability' Software quality is very important, especially for commercial and system software like Microsoft Office, Microsoft Windows and Linux. If software is faulty (buggy), it can delete a person's work, crash the computer and do other unexpected things. Faults and errors are called "bugs." Many bugs are discovered and eliminated (debugged) through software testing. However, software testing rarely – if ever – eliminates every bug; some programmers say that "every program has at least one more bug" (Lubarsky's Law). All major software companies, such as Microsoft, Novell and Sun Microsystems, have their own software testing departments with the specific goal of just testing. Software can be tested through unit testing, regression testing and other methods, which are done manually, or most commonly, automatically, since the amount of code to be tested can be quite large. For instance, NASA has extremely rigorous software testing procedures for many operating systems and communication functions. Many NASA based operations interact and identify each other through command programs called software. This enables many people who work at NASA to check and evaluate functional systems overall. Programs containing command software enable hardware engineering and system operations to function much easier together. 'License' The software's license gives the user the right to use the software in the licensed environment. Some software comes with the license when purchased off the shelf, or an OEM license when bundled with hardware. Other software comes with a free software license, granting the recipient the rights to modify and redistribute the software. Software can also be in the form of freeware or shareware. 'Patents' Software can be patented in some but not all countries; however, software patents can be controversial in the software industry with many people holding different views about it. The controversy over software patents is about specific algorithms or techniques that the software contains, which may not be duplicated by others and considered intellectual property and copyright infringement depending on the severity. 'Reference' Category:Software Engineering